The Effects of Foundation Stiffness on Surface Fault Rupture in Reverse Faults

Abstract

AbstractThe occurrence of intense earthquakes in cities placed near active faults is unavoidable. The characteristics of these earthquakes are different from those occurring in the sites placed in the far-field. After destructive earthquakes, such as Landers-California (1992), Kobe-Japan (1995), Chi-Chi-Taiwan (1999), Duzce and Kocaeli-Turkey (1999), engineering societies and scientific committees realized that these characteristics should be considered in the analysis and design of structures placed in near-faults. One of the destructive characteristics of near-fault earthquakes that has caused great loss of lives and severe structural damages is surface fault rupture. However, it was observed that some structures survived this phenomenon and the rupture path was changed and passed through the vicinity of structures without severe foundation damages. In most of the standards of seismic design of structures, this characteristic is denied; in some other standards, fault avoidance zones are considered to deal with surface rupture, but these zones are usually inadequate. In this investigation, the effect of foundation stiffness on the surface fault rupture path is studied using numerical studies. The possible effects of soil properties are considered via modeling 2 different soil mediums. Moreover, the mat foundations with different dimensional characteristics are modeled considering soil-foundation interaction. This FE study shows that the foundation stiffness has a significant effect on the rupture path; increasing stiffness of the foundation by increasing the thickness or decreasing the length, affects fault rupture path.